Metrology Point Selection for Lithography Alignment
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Solution Overview
Problem
Current lithographic processes face challenges in accurately measuring features on substrates due to the limited number of metrology points that can be measured without reducing throughput, leading to suboptimal alignment models and increased costs.
Innovation Solution
A method to determine a measurement subset of metrology point locations by identifying candidate locations, evaluating their informativity, and selecting those that maximize the level of informativity, thereby optimizing the measurement scheme without compromising throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of metrology points measured is increased to improve alignment model reliability, then measurement precision is improved, but throughput decreases and time is lost
Solution Approach 1:
The patent extracts only the most informative subset of metrology points from the complete set of potential measurement locations. By evaluating the informativity contribution of each candidate point and selecting only those that maximize model reliability, the system achieves high measurement precision with a reduced number of measurements, thereby maintaining throughput.
Solution Approach 2:
The patent changes the selection criterion for metrology points from uniform or random sampling to informativity-based selection. By introducing an evaluation metric that quantifies the contribution of each candidate point to model reliability, the system optimizes the measurement subset to achieve maximum precision with minimum measurements.
2Measurement precision
If the number of metrology points measured is increased to improve alignment model reliability, then measurement precision is improved, but the time required for measurement increases
Solution Approach 1:
The patent extracts only the most informative subset of metrology points from the complete set of potential measurement locations. By evaluating the informativity contribution of each candidate point and selecting only those that maximize model reliability, the system achieves high measurement precision with a reduced number of measurements, thereby reducing measurement time.
Solution Approach 2:
The patent performs preliminary evaluation of candidate metrology point locations to determine their informativity contribution before actual measurement. This pre-assessment allows the system to identify and select only the most valuable measurement points in advance, avoiding time-consuming measurements at less informative locations.
3Manufacturing precision
If the number of metrology points measured is increased to improve alignment model reliability, then manufacturing precision is improved, but throughput decreases
Solution Approach 1:
The patent extracts only the most informative subset of metrology points from the complete set of potential measurement locations. By evaluating the informativity contribution of each candidate point and selecting only those that maximize model reliability, the system achieves high manufacturing precision with a reduced number of measurements, thereby maintaining throughput.
Solution Approach 2:
The patent changes the selection criterion for metrology points from uniform or random sampling to informativity-based selection. By introducing an evaluation metric that quantifies the contribution of each candidate point to overlay performance, the system optimizes the measurement subset to achieve maximum manufacturing precision with minimum measurements.
Data Source
AI summary
A method of determining a measurement subset of metrology point locations which includes a subset of potential metrology point locations on a substrate. The method including identifying a plurality of candidate metrology point locations from the potential metrology point locations. A change in the level of informativity imparted by the measurement subset of metrology point locations which is attributable to the inclusion of that candidate metrology point location into the measurement subset of metrology point locations is evaluated for each of the candidate metrology point locations. The candidate metrology point locations which have the greatest increase in the level of informativity attributed thereto are selected for inclusion into the measurement subset of metrology point locations.